A radioreceptorassay of HCG-LH has been developed to study early normal and abnormal pregnancy before and after the missed period. A reference curve for the secretion of pregnancy specific HCG-LH-like material and HCG in patients, who later proved to be normal, will be established. This will permit the recognition of abnormalities and variations at the time of implantation in the first trimester which include multiple and ectopic pregnancy, abortion and mole. The high sensitivity and specificity of the method will provide evidence for the presence of subclinical abortion at the time of or prior to the onset of the first missed period. Steroid therapy for the treatment of threatened abortion, earlier than heretofore used, will be assessed. Since the assay also detects LH, it will be used for the recognition of the LH peak in cases of induced ovulation. The effectiveness of this assay for the early diagnosis of pregnancy to provide an accurate and early indication for miniabortion will be further evaluated.